The death toll from flooding in north-west Pakistan rose to 1,100 today as rescue workers struggled to save more than 27,000 people still trapped by the water.

The rescue effort was aided by a slackening of the monsoon rains that caused the worst flooding in decades in Khyber-Pakhtoonkhwa province. But as the waters started to recede, authorities began to understand the full scale of the disaster.

"Aerial monitoring is being conducted, and it has shown that whole villages have washed away, animals have drowned and grain storages have washed away," said Latifur Rehman, a spokesman for the provincial disaster management authority. "The destruction is massive."

The flooding, which the UN estimates has affected one million people nationwide, comes as the Pakistani government is grappling with a faltering economy and a war against the Taliban.

The US said yesterday it would provide Pakistan with $10m (£6.4m) in humanitarian assistance, a high-profile gesture at a time when the Obama administration is keen to dampen anti-American sentiment in the country.

But while Washington provided rescue boats, water filtration units and prefabricated steel bridges, its initiative faced competition on the ground from aid groups with alleged links to Islamist militants.

As Pakistani troops in helicopters dropped thousands of US-sponsored packaged meals to flood victims, food and medical services were also being offered in some of the hardest-hit areas by representatives from a charity allegedly linked to Lashkar-e-Taiba, the militant group blamed for the 2008 attacks in Mumbai.

"We are reaching people at their doorsteps and in the streets, especially women and children who are stuck in their homes," an activist with the Falah-e-Insaniat charity told the Associated Press.

The death toll could rise even higher because rescue workers have been unable to access certain areas, said Adnan Khan, a disaster management official. The military has deployed 30,000 troops who have helped rescue more than 20,700 people.

But almost 700 people had drowned in the Peshawar valley, which includes the districts of Nowshera and Charsadda, and 115 others were still missing yesterday.

The districts of Swat and Shangla have had more than 400 deaths, said Mujahid Khan, the head of rescue services for the Edhi Foundation, a private charity.

Residents of Swat were still trying to recover from a battle between the army and the Taliban last spring that caused widespread destruction and drove about two million people from their homes.

About a million of those are still displaced. In Swat alone, the floods have destroyed more than 14,600 houses and 22 schools, said Khan. Authorities have deployed 43 military helicopters and more than 100 boats to try to rescue some 27,300 people still trapped by the floods.

"All efforts are being used to rescue people stuck in inaccessible areas and all possible help is being provided to affected people," said Rehman.

But some residents were critical of the government's response.

"The flood has devastated us all, and I don't know where my family has gone," said Hakimullah Khan, a resident of Charsadda town whose wife and three children are missing.

"Water is all around and there is no help in sight," he said.

Sehar Ali Shah, who was among those rescued, said the authorities had provided no shelter that would allow them to stay until the floodwaters receded.

"My son drowned, but I don't see the government taking care of us," said Shah, after returning to his half-submerged house in the city of Nowshera.

"[It] has not managed an alternate place to shift us."

The flooding has also affected the central province of Punjab, where troops rescued more than 1,400 people trapped by rising water, said Brigadier Ahmad Waqas.

"We have lost everything: our houses, our crops, cattle," said Ahmad Hasan at a government relief camp in Taunsa Sharif district.

The threat of disease also loomed, as some some evacuees in the northwest arrived in camps with various ailments.

"There is now a real danger of the spread of waterborne diseases like diarrhoea, asthma, skin allergies and perhaps cholera in these areas," said Shaharyar Bangash, the head of operations in Khyber-Pakhtoonkhwa for World Vision, an international humanitarian group.

Some residents wondered how they would ever recover from such a disaster.

"I won't be able to cover my losses for 10 years," said Shair Dad, a timber shop owner in Nowshera who lost most of his wood in the floodwaters.